The development of new techniques - such as southern blotting, R-looping and molecular cloning - has played a major role in recent progress in our understanding of eukaryotic gene structure and regulation. We have developed another new technique, two dimensional restriction analysis, that will: 1) allow the purification and cloning of many interesting genes that were previously difficult or impossible to isolate; 2) provide a novel to l for testing certain models of development, and; 3) give new information concerning eukaryotic DNA organization. Two dimensional (2-D) restriction analysis is basically a DNA fractionation procedure that is currently capable of resolving the genome of a simple animal (e.g. Drosophila) into a pattern of DNA bands in agarose gels. The pattern of bands reflects the nucleotide sequence (arrangement of restriction sites) of the genome and therefore interesting structural features of the pattern (e.g. intense bands, faint bands and horizontal lines) reveal useful information concerning DNA organization. Furthermore, by combining 2-D analysis with Southern blotting, the arrangement of the recently discovered class of dispersed repeated gene families will be studied. Useful information will be obtained by comparing 2-D patterns of DNAs from different sources. For example, bands with specific genes will be identified by comparing the 2-D patterns of DNAs from wild type and mutants with deletions, or duplications of known genes. (The corresponding band(s) will be missing, or intensified in the mutant patterns).